Inferior Conjunction - the instant when a planet passes between Earth and the Sun (Mercury or Venus)

Superior Conjunction - the instant when a planet passes on the opposite side of the Sun from Earth (Mercury or Venus)

Greatest Elongation - elongation is the apparent angle between a planet and the Sun as seen from Earth; during eastern elongation (E), the planet appears as an evening star; during western elongation (W), the planet appears as a morning star

Opposition - the instant when a planet appears opposite the Sun as seen from Earth

Conjunction - the instant when a planet appears closest the Sun as seen from Earth

Occultation - the Moon occults or eclipses a star or planet

Ascending Node - the point where a planet crosses from the southern to northern portion of its orbit

Descending Node - the point where a planet crosses from the northern to the southern portion of its orbit